Strangeness Production at COSY - (Indico) · Strangeness Production at COSY September 07, 2015...

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Strangeness Production at COSY

September 07, 2015 Florian Hauenstein HYP2015, Sendai, Japan

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Physics Program at COSYNon-perturbative QCD in the up, down and strange sector

Structure of hadronsnucleonshyperonsmesons

Dynamics and interactionsnucleon-nucleon (NN)nucleon-hyperon (NY )nucleon-mesonmeson-nucleus, in medium effects

Symmetries and symmetry breakingchiral symmetryisospin and charge symmetry in reactionsdiscrete symmetries in meson decays

September 07, 2015 Florian Hauenstein Slide 2

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COSY FacilityCOoler SYnchroton

Circumference: 184mBeam momentum: 0.3GeV/c -3.7GeV/cStochastic and electron cooling(Un-)Polarized proton anddeuteron beams


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COSY-TOF: Physics Program

Meson production in pp collisionsStudy of pp → ppγExclusive hyperon production in pN → NKY with polarizedand unpolarized beams

production mechanism of associated strangenessNY interaction through final state interaction (FSI)NΛ− NΣ coupled channel effectnucleon excited states (N∗ resonances)polarization observables

Recent studies:~pp → pKΛ at pbeam = 2.7GeV/c with ≈ 78% polarization~pp → pKΛ at pbeam = 2.95GeV/c with ≈ 88% polarizationpn→ NKΛ at pbeam = 2.95GeV/c


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COSY-TOF DetectorTime Of Flight

STTRing

Quirl

Barrel

Start SQT

Calorimeter

p

p

K+

-

pBeam

3m

Features:

Full phase space coverage

Clear signature forpKΛ→ pK pπ(2 primary and2 secondary tracks)

Primary and delayedhyperon decay vertex(cτ(Λ) = 7.89 cm)

Latest Measurements of ~pp → pKΛ:

2.95GeV/c with (61.0± 1.7) % polarization → 42,000 events

2.95GeV/c with (87.5± 2.0) % polarization → ∼ 132,000 events

2.70GeV/c with (77.9± 1.2) % polarization → ∼ 220,000 eventsSeptember 07, 2015 Florian Hauenstein Slide 5

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Physics of ~pp → pKΛ

Described by meson exchange models (no perturbative QCD)Which kind of meson exchangeRole of N∗ resonances

p

p

K

K

p

Λ p

p

π

K

Λ

p p

p

π

K

Λ

p

N*

[MeV/c^2]Λp m2060 2080 2100 2120 2140 2160 2180 2200 2220 2240 2260

)2N

/A/(

2MeV

/c

500

1000

1500

2000

2500

3000

3500

]2 [MeV/cΛp m2060 2080 2100 2120 2140 2160 2180 2200 2220 2240 2260

A

00.10.2

0

2.95GeV/c

nΣ+ pΣ0

M. Roeder, Eur. Phys. J. A49, 157 (2013)

pΛ− NΣ coupled channel (cusp)effect

pΛ final state interaction (FSI)

Connection to pΛ interaction→ Parameter: scattering length a

limk→0

σpΛ→pΛ = 4πa2


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Determination of pΛ Scattering LengthMethod from A. Gasparyan et al., Phys. Rev. C69, 034006 (2004)

Extraction of pΛ scattering length a from the shape of thefinal state interaction (FSI)No further theoretical assumption necessaryKnown theoretical precision (0.3 fm)Spin resolved measurement via suitable polarization observable

[MeV/c^2]Λp m2060 2080 2100 2120 2140 2160 2180 2200 2220 2240 2260

)2N

/A/(

2MeV

/c

500

1000

1500

2000

2500

3000

3500

]2 [MeV/cΛp m2060 2080 2100 2120 2140 2160 2180 2200 2220 2240 2260

A

00.10.2

0

2.95GeV/c

nΣ+ pΣ0

COSY-TOF measurement at2.95GeV/c (42,000 events)M. Roeder et al., Eur. Phys. J. A49, 157 (2013)

Effective scattering lengthaeff = (−1.25± 0.08stat. ± 0.3theo.) fm

Large systematic error (1 fm) due tokinematical reflection of N∗ resonance


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Dalitz Plot Dependence on Beam MomentumNΣFSI

COSY-TOF Coll., Phys. Lett. B688, 142 (2010)

Contributions of N∗ change with beam momentaExpected smaller systematic effect on FSI for 2.7GeV/c?

⇒ Comparison of results from the recent data at 2.7GeV/c (∼132,000 events) and 2.95GeV/c (∼ 220,000 events)


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~pp → pKΛ Dalitz Plot

]4/c2 [GeV2Λp m

4.2 4.3 4.4 4.5 4.6 4.7

]4

/c2

[G

eV

2Λ

K

m

2.6

2.65

2.7

2.75

2.8

2.85

2.9

2.95

3

0

50

100

150

200

250

300

350

400

preliminary

2.7GeV/c

Hauenstein, PhD Thesis, 2014

2.7GeV/cMonte Carlo acceptance

2.95GeV/c

preliminaryJowzaee, PhD Thesis, 2014

Full phase space acceptance

Reconstruction efficiency relativelyflat

Strong pΛ final state interaction forboth data sets

More substructures for 2.95GeV/cSeptember 07, 2015 Florian Hauenstein Slide 9

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Effective pΛ Scattering Length

/ ndf 2χ 44.82 / 36 0C 0.0317± -0.1393 1C 7.663e+03± 1.211e+05 2C 3.470e+03± 4.158e+06

)2 (MeV/cΛp m2060 2080 2100 2120 2140 2160

))2 (

nb

/(M

eV/c

Λp

/d

mσ

d

0

50

100

/ ndf 2χ 44.82 / 36 0C 0.0317± -0.1393 1C 7.663e+03± 1.211e+05 2C 3.470e+03± 4.158e+06

/ ndf 2χ 44.82 / 36 0C 0.0317± -0.1393 1C 7.663e+03± 1.211e+05 2C 3.470e+03± 4.158e+06

preliminary

2.7GeV/c

)2 (MeV/cΛpm2060 2080 2100 2120 2140 2160

(ar

b. u

nit

s)2 |

A~ |

0

2

4

6 / NDF = 1.252χ = -1.39e-01 + 3.06e-02 - 3.25e-020C

= 1.21e+05 + 7.99e+03 - 7.26e+031C

= 4.16e+06 + 3.32e+03 - 3.58e+032C

2.7GeV/c

preliminary

fit limit fit limitdσ

dmpΛ/PS

Parametrization: dσdmpΛ

= PS ·∣∣∣A(FSI )

∣∣∣2 = PS · exp[C0 + C1

m2pΛ−C2

]aeff = (−1.38+0.04

−0.05stat. ± 0.12syst. ± 0.3theo.) fm (preliminary)

Compatible with the result at 2.95GeV/c(aeff = (−1.25± 0.08stat. ± 0.3theo.) fm)

Systematic error mainly due to influence of N∗ resonances→ but weaker than for 2.95GeV/c (1 fm)


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Spin Triplet pΛ Scattering Lengthsee Appendix B in Gasparyan et al., Phys. Rev. C69, 034006 (2004)

pΛ in S-wave and kaon in P-wave ⇒ pΛ in spin tripletconfiguration due to parity and angular momentum conservation

Kaon analyzing power AKy sensitive to kaon P-wave contribution

AKy (X ,mpΛ) ≈ α(mpΛ)P1

1 (X ) + β(mpΛ)P12 (X )

Kaon P-wave contribution proportional to AKy (cos θ = 0) = −α

→ α gives relative contribution of spin triplet scattering→ Measurement of α dependence on mpΛ to determine spin tripletscattering length using the formula

|A(FSI )t(mpΛ)|2 = −α(mpΛ) ·∣∣∣A(FSI )eff(mpΛ)

∣∣∣2September 07, 2015 Florian Hauenstein Slide 11

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Kaon Analyzing Power at 2.7GeV/cFit with associated Legendre polynomials and dependence on mpΛ

)2 (MeV/cΛpm2060 2080 2100 2120 2140 2160

Leg

end

re p

oly

no

mia

l co

effi

cien

ts

-0.2

-0.1

0

0.1

0.2 α

β

)CMSKθcos(

-1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1

kao

n a

nal

yzin

g p

ow

er

-0.1

0

0.1

0.2

)2

1 P• β + 11 P• αfit (

)θ (cos11 P• α

)θ (cos2

1 P• β

/ NDF = 0.752χ

0.005± = -0.143 α 0.004± = 0.036 β

preliminary

preliminary

full data

Reasonable fit of analyzing power by AKy = αP1

1 + βP12

β decreases for higher mpΛ masses (expected due to lowerkaon momentum)α non zero for low mpΛ mass → extraction of spin tripletscattering length possible → publication in preparation


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Analyzing Power of Final State Particles

)CMSpθcos(

1 0.5 0 0.5 1

pro

ton

an

aly

zin

g p

ow

er

0.15

0.1

0.05

0

0.05

0.12.95 GeV/c [Jow14]

2.7 GeV/c

preliminary)

CMS

Λθcos(

1 0.5 0 0.5 1

an

aly

zin

g p

ow

er

Λ

0.2

0.15

0.1

0.05

0

0.05

0.1

0.152.95 GeV/c [Roe11]2.95 GeV/c [Jow14]2.75 GeV/c [Piz07]2.7 GeV/c

preliminary

)CMS

Kθcos(

1 0.5 0 0.5 1

ka

on

an

aly

zin

g p

ow

er

0.1

0

0.1

0.2

0.3

2.95 GeV/c [Roe11]

2.95 GeV/c [Jow14]

2.75 GeV/c [CTOF07,Piz07]

2.7 GeV/c

preliminary Proton and kaon analyzingpower: Same behavior fordifferent momentaΛ analyzing power: forcos(θCMS

Λ > 0) differentbehavior


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Λ PolarizationDetermination Principle

pBeam

scatteringplane

nsp = pBeam x pΛ

pp**

pπ**

pΛθ**

Λ polarization along nsp axisMeasurement via selfanalyzing Λ decayDistribution of decay protons:I = I0(1 + αPΛ cos θ∗∗)

α = 0.642± 0.013 (weakasymmetry parameter)Determination by "weightedsum method" [D. Besset et al., Nucl.

Instr. Meth. 166, 515 (1979)]

PΛ =1α

∑Ni=0 cos(θ

∗∗i )∑N

i=0 cos2(θ∗∗i )


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Results for the Λ Polarization

)CMS

Λθcos(

1 0.8 0.6 0.4 0.2 0 0.2 0.4 0.6 0.8 1

ΛP

0.4

0.3

0.2

0.1

0

0.1

0.2

0.3

0.4

2.95 GeV/c [Roe11]

2.75 GeV/c [Piz07]

2.7 GeV/c

preliminary

[Roe11]M. Roeder, PhD Thesis,University Bochum, 2012

[Piz07]C. Pizzolotto, PhD Thesis,University Erlangen, 2007

2.7GeV/cHauenstein, PhD Thesis,University Erlangen, 2014

Λ polarization changes signFurther study by fitting of associated Legendre polynomials toavailable COSY-TOF data


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Λ PolarizationAssociated Legendre Polynomials Fits

)CMS

Λθcos(

1 0.8 0.6 0.4 0.2 0 0.2 0.4 0.6 0.8 1

ΛP

0.4

0.3

0.2

0.1

0

0.1

0.2

0.3

0.4

)2

1 P• 2

+ C1

1 P• 1

fit (C

)θ (cos1

1 P• 1

C

)θ (cos2

1 P• 2

C

/ NDF = 1.982χ

0.008± = 0.002 1

C

0.006± = 0.133 2

C

2.7GeV/c

preliminary

)CMS

Λθcos(

1 0.8 0.6 0.4 0.2 0 0.2 0.4 0.6 0.8 1

ΛP

0.2

0.1

0

0.1

0.2

0.3)

2

1 P• 2

+ C1

1 P• 1

fit (C

)θ (cos1

1 P• 1

C

)θ (cos2

1 P• 2

C

/ NDF = 0.792χ

0.036± = 0.013 1

C

0.027± = 0.030 2

C

2.75 GeV/c [Piz07]

preliminary

)CMS

Λθcos(

1 0.8 0.6 0.4 0.2 0 0.2 0.4 0.6 0.8 1

ΛP

0.2

0.1

0

0.1

0.2

0.3

)2

1 P• 2

+ C1

1 P• 1

fit (C

)θ (cos1

1 P• 1

C

)θ (cos2

1 P• 2

C

/ NDF = 2.312χ

0.019± = 0.020 1

C

0.014± = 0.066 2

C

2.95 GeV/c [Roe11]

preliminary

)CMS

Λθcos(

1 0.8 0.6 0.4 0.2 0 0.2 0.4 0.6 0.8 1

ΛP

0.4

0.2

0

0.2

0.4

)2

1 P• 2

+ C1

1 P• 1

fit (C

)θ (cos1

1 P• 1

C

)θ (cos2

1 P• 2

C

/ NDF = 0.752χ

0.053± = 0.012 1

C

0.040± = 0.188 2

C

3.2 GeV/c [Schr03]

preliminary


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Λ PolarizationAssociated Legendre Polynomials Contributions

[GeV/c]beam

p2.7 2.8 2.9 3 3.1 3.2

mag

nit

ud

es [

arb

. u

nit

s]

2 a

nd

C1

C

0.2

0.1

0

0.1

0.2 1C

2C

preliminary

As expected C1 compatible with zero for all beam momentaC2 strong variation with beam momentum. Linear increase?No theoretical calculations available


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Summary

High statistics measurement with full phase space acceptance of the~pp → pKΛ reaction at 2.7GeV/c and 2.95GeV/cDalitz plot

Strong pΛ final state interactionStrength of enhancement at NΣ threshold (cusp effect) varieswith beam momentum

Scattering length at 2.7GeV/caeff = (−1.38+0.04

−0.05stat. ± 0.12syst. ± 0.3theo.) fm (preliminary)Kaon analyzing power: α not vanishing for low mpΛ massesFirst model independent determination of at possible

Λ analyzing powerDeviation for different beam momenta for cos θCMS

Λ > 0Λ polarization

Strong variation with beam momentumFit with Legendre polynomials → Solely described by P1

2September 07, 2015 Florian Hauenstein Slide 18

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Outlook

Detailed study of the NΣ cusp effect at 2.95GeV/cCombined Partial Wave Analysis of pp → pKΛ at differentbeam momenta including data from DISTO and HADES/FOPIPublication of spin triplet scattering length at from pΛ finalstate interaction (September - October)Publication of polarization observables (PΛ,Ay ,DNN)→ Method paper submitted to NIM (arXiv:1508.04908)


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Backup Slides


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pΛ−NΣ Cusp

]2[GeV/cΛpM2 2.05 2.1 2.15 2.2 2.25 2.3

μ[Λp

/dM

σd

0

20

40

60

80

100

120

140 3.05GeV/cCOSY-TOF Coll., Eur. Phys. J. A49, 41 (2013)

Cusp described by Flattedistribution

Angular distributions in cuspregion point to S-wave inK − pΣ and subsequent Λ− p

In preparation: Study of cusp at2.95GeV/c

Reasonable description of spectrum byFSI + cusp(Flatte) + N∗ reflections

Further theoretical description necessary

/indfi2χ 226.8i/i163i

NΣg i0.180±1.253i

[GeV]irm i0.02±2.31i]i2[GeV0ΓC* i0.0241±0.3106i

]i-1[GeV0

c i0.0000334±0.0007869i]i2[GeV2c i0.001±3.713i

0a i0.08156±0.08079i

1a i0.00424±0.03065i

2a i0.0162±0.0115i

]i2[GeV/cΛinvariantimassip

2.05 2.1 2.15 2.2 2.25yi

eld

i[ar

b.iu

nit

s]

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6/indfi2χ 226.8i/i163i

NΣg i0.180±1.253i

[GeV]irm i0.02±2.31i]i2[GeV0ΓC* i0.0241±0.3106i

]i-1[GeV0

c i0.0000334±0.0007869i]i2[GeV2c i0.001±3.713i

0a i0.08156±0.08079i

1a i0.00424±0.03065i

2a i0.0162±0.0115i

2.95GeV/c

preliminarydσ

dmp

Λ/PS

Jowzaee, EPJA, in preparation


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Dalitz Plot Projections on mpΛ

]4/c2 [GeV2Λpm

4.2 4.3 4.4 4.5 4.6 4.7

)]4

/c2

b/(

GeV

µ [

2

Λp

/d m

σd

0

10

20

30 threshold

+Σn

threshold0

Σp

preliminary

2.7GeV/c

Hauenstein, PhD Thesis, 2014

2.95GeV/c

preliminaryJowzaee, PhD Thesis, 2014

Green: Scaled phase spacedistributionSmall enhancement at NΣthreshold

Brown: Scaled phase spacedistributionLarge enhancement at NΣthreshold compared to2.7GeV/c


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Effective pΛ Scattering Length for mKΛ Regionssee M. Roeder et al., Eur. Phys. J. A49, 157 (2013)

]4/c2 [GeV2Λpm

4.3 4.4 4.5 4.6 4.7 4.8 4.9 5 5.1

]4/c2

[G

eV2

ΛK

m

2.6

2.7

2.8

2.9

3

3.1

3.2

3.3

ΣN

N*

ΣK

upper regionlower region

2.95GeV/c

]2 [MeV/cΛpm2050 2060 2070 2080 2090 2100 2110

[ar

bit

rary

un

its]

2|M

|

0

1

2

3

4

5

6

7

8

9

10

all data

upper region +1.5 units

lower region +1.5 units

aeff = (−1.25± 0.08stat. ± 0.3theo.) fm(full data)aeff = (−2.06± 0.16stat. ± 0.3theo.) fm(upper region)aeff = (−0.86± 0.06stat. ± 0.3theo.) fm(lower region)

Strong influence of N∗ resonancesError in the order of 1 fm


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α Measurement at 2.95GeV/csee M. Roeder et al., Eur. Phys. J. A49, 157 (2013)

*)Kθ cos(-1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1

An

alys

ing

Po

wer

-0.1

-0.05

0

0.05

0.1

0.15

0.2

0.25

Associated Legendre Polys

0.013)± (-0.145 × 11P

0.010)± (0.065 × 12P

/NDF = 0.542χ

]2 [MeV/cp - mΛ - mΛp m0 20 40 60 80 100 120 140 160 180 200 220

coef

fici

ents

0

0.05

0.1

0.15

0.2

0.25

Unexpected: α is < 11% (3σ) for low invariant mass→ no sufficient precision for extraction of spin triplet pΛscattering lengthβ behavior reasonable

→ Work in progress: Analysis of additional measurement at2.95GeV/c to reduce statistical error


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Results from the Measurement at 2.7GeV/cDalitz Plot Slices

]4/c2 [GeV2Λp

m4.2 4.3 4.4 4.5 4.6 4.7

]4

/c2

[G

eV

2Λ

K

m

2.6

2.65

2.7

2.75

2.8

2.85

2.9

2.95

3

0

50

100

150

200

250

300

350

400

> 0.5Λp

pKθcos

]4/c2 [GeV2Λp

m4.2 4.3 4.4 4.5 4.6 4.7

]4

/c2

[G

eV

2Λ

K

m

2.6

2.65

2.7

2.75

2.8

2.85

2.9

2.95

3

0

50

100

150

200

250

300

350

400

> 0Λp

pKθ0.5 > cos

]4/c2 [GeV2Λp

m4.2 4.3 4.4 4.5 4.6 4.7

]4

/c2

[G

eV

2Λ

K

m

2.6

2.65

2.7

2.75

2.8

2.85

2.9

2.95

3

0

50

100

150

200

250

300

350

400

> 0.5Λp

pKθ0 > cos

]4/c2 [GeV2Λp

m4.2 4.3 4.4 4.5 4.6 4.7

]4

/c2

[G

eV

2Λ

K

m

2.6

2.65

2.7

2.75

2.8

2.85

2.9

2.95

3

0

50

100

150

200

250

300

350

400

< 0.5Λp

pKθcos


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Effective pΛ Scattering Length for Dalitz Plot SlicesLikelihood Distributions

a [fm]

1.55 1.5 1.45 1.4 1.35 1.3

lik

eli

ho

od

pro

ba

bil

ity

[a

rb.

un

its

]

0

2

4

6

constant 6.495

mean [fm] 1.407

sigma [fm] 0.037

> 0.5Λp

pKθcos

preliminarya [fm]

1.2 1.15 1.1 1.05

lik

eli

ho

od

pro

ba

bil

ity

[a

rb.

un

its

]

0

2

4

6

8 constant 7.635

mean [fm] 1.139

sigma [fm] 0.027

> 0Λp

pKθ0.5 > cos

preliminary

a [fm]

1.3 1.25 1.2 1.15 1.1

lik

eli

ho

od

pro

ba

bil

ity

[a

rb.

un

its

]

0

2

4

6

constant 6.861

mean [fm] 1.186

sigma [fm] 0.029

> 0.5Λp

pKθ0 > cos

preliminarya [fm]

1.3 1.25 1.2 1.15

lik

eli

ho

od

pro

ba

bil

ity

[a

rb.

un

its

]

0

2

4

6

constant 6.795

mean [fm] 1.244

sigma [fm] 0.025

< 0.5Λp

pKθcos

preliminarySeptember 07, 2015 Florian Hauenstein Slide 26

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CMS Distributions for 2.7 GeV/c

1 0.5 0 0.5 1

b/s

r]

µ [

Ω / d

σ

d

0.5

1

CMSpθcos

1 0.5 0 0.5 1

RE

. [%

] •

AC

.

0

5

10

15

preliminary

p

1 0.5 0 0.5 1

b/s

r]

µ [

Ω / d

σ

d

0.5

1

CMSΛθcos

1 0.5 0 0.5 1

RE

. [%

] •

AC

.

0

5

10

15

preliminary

Λ

1 0.5 0 0.5 1

b/s

r]

µ [

Ω / d

σ

d

0.5

1

CMS

Kθcos

1 0.5 0 0.5 1

RE

. [%

] •

AC

.

0

5

10

15

preliminary

KDistributions almostsymmetricSmall deviations at boardersdue to acceptance correction


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Formulas for Scattering Length Extraction

Parametrization of pΛ invariant mass spectrum

dσdmpΛ

= PS · |AFSI(mpΛ)|2 = PS ·exp

[C0 +

C1

m2pΛ − C2

]. (1)

a dependence on C1 and C2

at(C1,C2) = −~c2C1 ×

√(m2

0mpmΛ

)(m2

max −m20)

(m2max − C2)(m2

0 − C2)3

with m0 = mp + mΛ and mmax = m0 + 40MeV/c2

Spin Triplet Amplitude

|At(mpΛ)|2 = −α ·∣∣∣Aeff(mpΛ)

∣∣∣2September 07, 2015 Florian Hauenstein Slide 28

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Analyzing PowerDetermination Principle

Angular distribution for particles with polarization PY :( dσdΩ )pol. = ( dσ

dΩ )0 · (1 + ANPN) = ( dσdΩ )0 · (1 + ANPY cosφ)

L

RPY AN

AN(cos θCMS) =εLR(cos θCMS, φ)

cos(φ) · pB

Azimuthal left-right asymmetry

εLR(cos θCMS, φ) =L(θCMS

p ,φ)−R(θCMSp ,φ)

L(θCMSp ,φ)+R(θCMS

p ,φ)

Count ratesL(θCMS

p , φ)) =√N+(φ) · N−(φ+ π) and

R(θCMSp , φ) =

√N+(φ+ π) · N−(φ)

Beam polarization pB


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Experimental SetupStraw Tube Tracker (STT)

2704 straw tubes (l = 1m, d = 1 cm)arranged in 13 double layers

Every double layer is shifted by 60 angle tothe other for 3D track reconstruction

Ar : CO2 gas mixture with ratio 8 : 2 at1.2 bar overpressure

Drift time information used for track to wiredistance

Obtained averaged spatial resolutionσ = (137± 9) µm


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Event ReconstructionSteps for pp → pKΛ reconstruction

1 Track finding (Hough transformation) and fitting2 Vertex finding and fitting3 Geometric fit of pp → pKΛ event topology4 Kinematic fit of pp → pKΛ→ Kinematically complete events→ pΛ mass resolution σ = 1.1MeV/c2

u’ [cm]30 20 10 0 10 20 30

z [

cm

]

0

10

20

30

40

50

60

v’ [cm]30 20 10 0 10 20 30

z [

cm

]

0

10

20

30

40

50

60

w’ [cm]30 20 10 0 10 20 30

z [

cm

]

0

10

20

30

40

50

60


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Event Selection

Selection criteriaχ2kin.fit < 5

Λ decay length > 3 cm](Λ, decayproton) > 2

Monte Carlo simulationsLow background from otherreactions (pp → pKΣ0 < 1%)Reconstruction efficiency∼ 15%

/ NDFK

2χ0 2 4 6 8 10

arb

itra

ry u

nit

s310

410

510

ΛpK

0ΣpK

Missing Energy [MeV]100 80 60 40 20 0 20 40 60 80 100

En

trie

s / B

in

0

5000

10000

15000

20000

25000

30000all selections

/ NDF < 50K

2χ


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Future of COSY

Test facility for FAIR (Facility for Antiproton and Ion Research) atGSI in Darmstadt, Germany

Accelerator components → HESR at FAIRDetector components → PANDA, CBM, ...

Measurement of charged particle EDM (Electric Dipole Moment)

EDMs are candidates to solvematter-antimatter asymmetry

Measurement of proton and deuteron EDMwith one dedicated ring → JEDI collaboration

Precursor experiments with actual COSY ring


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Spin Triplet Scattering Length atPreliminary from Hauenstein, PhD Thesis, 2014

/ ndf 2χ 73.43 / 36

p0 0.0432± 0.1482

p1 1.135e+04± 1.318e+05

p2 5.202e+03± 4.151e+06

]2 [MeV/cΛp m

2060 2080 2100 2120 2140 2160

)]2

[n

b/(

MeV

/cΛ

p

/d m

σd

0

50

100

/ ndf 2χ 73.43 / 36

p0 0.0432± 0.1482

p1 1.135e+04± 1.318e+05

p2 5.202e+03± 4.151e+06

/ ndf 2χ 73.43 / 36

p0 0.0432± 0.1482

p1 1.135e+04± 1.318e+05

p2 5.202e+03± 4.151e+06

preliminary

/ ndf 2χ 9.086 / 5p0 0.2730± 0.7746 p1 4.625e+04± 4.931e+04 p2 3.276e+04± 4.186e+06

]2 [MeV/cΛp m

2060 2080 2100 2120 2140 2160

) [a

rb. u

nit

s]

Λp

(m

Kα

*

Λp

/d

mσ

d

0

10

20

/ ndf 2χ 9.086 / 5p0 0.2730± 0.7746 p1 4.625e+04± 4.931e+04 p2 3.276e+04± 4.186e+06

/ ndf 2χ 9.086 / 5p0 0.2730± 0.7746 p1 4.625e+04± 4.931e+04 p2 3.276e+04± 4.186e+06

preliminary

fit limit

Rebin

×(−αK )

Parametrization: dσdmpΛ

= Phasespace · exp[p0 + p1

m2pΛ−p2

]at = (−1.31+0.32

−0.49stat. ± 0.3theo. ± 0.16syst.) fm (very preliminary)

First direct determination of atComparison:

at = (−1.6+1.1−0.8) fm (Λp elastic scattering)

at = −1.54 fm (theoretical calculation [NPA 915, 24-58 (2013)])September 07, 2015 Florian Hauenstein Slide 34

Strangeness Production at COSY - (Indico) · Strangeness Production at COSY September 07, 2015...

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